Method for whetting files, rasps, and the like



Patented Sept. 19, 1939 PATENT OFFICE METHOD FOR wm-z'r'rmo mas, misrs,AND run mm Emanuele Zoppi,

Genova. Italy No Drawing. Application October 18, 1937, Se-

rlal No..169,753. In Germany November 26,

This invention relates to a method for whetting filgsl, rasps and thelike by etching by means of It has already been previously proposed todip files to be whetted into an acid bath without preliminary treatment.This method has the disadvantage that the files were considerablyreduced in weight, whilst the whettlng obtained only lasted for a veryshort time. This method is therefore not of practical value. Accordingto the present invention the grease is first removed from files bytreating them in an alkaline bath, they are then treated in a bath ofhydrochloric acid, then in a bath of nitric acid and subsequently in abath of hydrochloric acid, whereupon any acid which may be adheringthereto is neutralised.

' The advantage of the new method resides in the fact that the bathswhich are used can be produced at low costs, that the files do not losein weight as a result of the treatment, and the method can be carriedout byfan unskilled workman. By means of the new method it is possibleto obtain in an economical manner sharp g5 and resistant teeth. Themethod may be carried out for example as follows.

For the removal of grease there is used a soda lye containing 50 g.caustic soda (NaOI-I) to one litre of water. In this lye the files areboiled for 80 about half an hour. The files are then removed from thelye and rinsed in water and brushed.

The files are then placed into a second bath consisting of 50 parts byweight commercial hydrochloric acid and 50 parts by weight of water. Thefiles are allowed to remain in this bath for 12 hours without theapplication of heat.

In this bath all adhering substances are removed and the surface isprepared for the succeeding third bath in which the files after havingbeen again rinsed and brushed are placed.

This third bath may be regarded as the renewing bath, it consists of 20parts by weight of nitric acid of 42 B. and 80 parts by weight of water.The files are allowed to remain in this 4!! bath for from 5-10 minuteswithout the applica tion of heat.

During the first moments there are formed fine bubbles which adhere tothe points of the teeth, enclose these and protect them against theaction of the acid. After 2-3 minutes the bubbles disappear and the bathcan attack the whole file. It is important during the treatment in thethird bath to repeatedly withdraw the files therefrom and to againimmerse them therein.

us After treatment in the third bath the files are 4 Claims. 01. -24)again washed and brushed. They are then placed for a period of 5-10minutes into a fourth bath which has the same composition as the secondbath. After rinsing and brushing the files are treated in a fifth bathwhich consists of water 5 and unslaked lime.

For this purpose there are used 5 litre of water and about 100 g.unslaked lime (09.0). It is sufiicient if the files are allowed toremain in this bath for about 10-20 minutes. They may howit) ever beallowed to remain, therein for a longer time (hours or days).

After treatment the files are again washed and brushed. They are thendried for example in saw-dust or by means of an air current and finallyl5 greased, preferably with mineral oil.

The washing of the files between the treatments in the separate baths ispreferably effected in hot water. Further it is preferable when takingthe files from one bath to immediately placethem 20 into the washingwater and from the washing water immediately into the next bath so thaton the passage from one bath to the other they are not exposed to theair for too long a period of time.

The files are preferably placed into the baths in a vertical position.

I claim:

1. The method of sharpening files, rasps and the like, which comprisesthe following steps in 30 the order mentioned. viz: first, subjectingthe articles to the de-greasing action of a boiling alkaline bathconsisting of 50 g. of NaOI-I to one litre of water; second, removingthe articles from the alkaline bath and rinsing them in water; third,placing the rinsed articles in a bath consisting of approximately equalparts by weight of hydrochloric acid and water, for about twelve hours,at normal temperature: fourth, removing the articles from thehydrochloric acid bath and 40 again rinsing them in water; fifth,placing the rinsed articles in a bath consisting of twenty parts byweight of nitric acid of 42 B. and eighty parts by weight of water, forfrom five to ten minutes, at normal temperature; sixth, remov- 45 ingthe articles from the nitric acid bath and after rinsing the same,neutralizing any adhering acid in a milk of limebath.

' 2. The method of sharpening files, rasps and the like, which comprisesthe following steps in 60 the order mentioned, viz: first,subjecting'the articles to the de-greasing action of a boilingv alkalinebath consistingof 50 g. of NaOI-I to one litre of water; second,removing the articles from the alkaline bath and rinsing them in water;so

third, placing the rinsed articles in a bath consisting of approximatelyequal parts by weight of hydrochloric acid and water, for about twelvehours, at normal temperature; fourth, removing the articles from thehydrochloric acid bath and again rinsing them in water; fifth, placingthe rinsed articles in a bath consisting of twenty parts by weight ofnitric acid of 42 B. and eighty parts by weight of water, for fromfive-to ten minutes, at normal temperature; sixth, removing the articlesfrom the nitric acid bath and after rinsing the same, placing thearticles again in a. hydrochloric acid bath like that of the third thelike, which comprises the following steps in the order mentioned, viz:first, subjecting the articles to the de-greasing action of a boilingalkaline bath consisting of g. of NaOH to one litre of water; second,removing the articles from the alkaline bath and rinsing them in water;third, placing the rinsed articles in a bath consisting of approximatelyequal parts by weight of hydrochloric acid and water, for about twelvehours, at normal temperature; fourth removing the articles from thehydrochloric acid bath and again rinsing them in water; firth, placingthe rinsed articles in a bath consisting of twenty parts by weight ofnitric acid of 42 B. and eighty parts by weight of water, for from fiveto 4. The method of sharpening flies, rasps and the like, whichcomprises the following steps in the order mentioned, viz: first,subjecting the articles to the de-greasing action of a boiling alkalinebath consisting of 50 g. of NaOH to one litre of water; second, removingthe articles from the alkaline bath and rinsing them in water; third,placing the rinsed articles in a bath consisting of approximately equalparts by weight of hydrochloric acid and water, for about twelve hours,at normal temperature; fourth, removing the articles from thehydrochloric acid bath and'ag'ain rinsing them in water; fifth placingthe rinsed articles in a bath consisting of twenty parts by weight ofnitric acid of 42 B. and eighty parts by weight of water, for from fiveto ten minutes, at normal temperature; sixth, removing the articles fromthe nitric acid-bath and after rinsing the same, placing the articlesagain in a hydrochloric acid bath like that of the third step above;seventh, removing the articles from the last acid bath and after rinsingthe articles, neutralizing any acid adhering there-

